Whilst the primary focus of absorbent articles, in particular feminine hygienic absorbent articles like sanitary napkins and pantiliners, remains the ability of these articles to absorb and retain fluids, another important area of development in this field is the control of odorous compounds contained within the absorbent articles during their use.
The presence and detection of malodorous compounds from absorbent articles during their use, particularly those associated with menstruation may cause the wearer of these articles embarrassment. Thus, the prevention of the detection of malodor from such articles is highly desirable too.
In use, the absorbent articles are known to acquire a variety of compounds, for example volatile fatty acids (e.g. isovaleric acid), ammonia, amines (e.g. triethylamine), sulphur containing compounds (e.g. mercaptans, sulphides), alcohols, ketones and aldehydes (e.g., furaldehyde) which release unpleasant odors. These compounds may be present in the bodily fluid or may be developed by chemical reactions and/or any fluid degradation mechanisms once the bodily fluid is absorbed into the absorbent article like for example a feminine hygienic absorbent article. In addition bodily fluids usually contain microorganisms and/or enzymes that can also generate malodorous by products as a result of degradation mechanisms like putrefactive degradation, acid degradation, proteins degradation, fat degradation and the like.
Various odor control materials have been disclosed in the art to combat some of the unpleasant odors referred to above. Indeed solutions have been provided that use different technical approaches like masking, i.e., covering the odor with a perfume, or absorbing the odor already present in the bodily fluids and those generated after degradation, or preventing the formation of the odor.
Most of the focus in the prior art is found on the odor absorption technology. Examples of these types of compounds include activated carbons, clays, zeolites, silicates, cyclodextrine, ion exchange resins and various mixture thereof as for example described in EP-A-348 978, EP-A-510 619, WO 91/12029, WO 91/11977, WO 89/02698, and/or WO 91/12030. All of these types of odor control agents are believed to control odor by mechanisms whereby the malodorous compounds and their precursors are physically absorbed by the agents and thereby hinder the exit of the odor from articles like absorbent articles. However, such mechanisms are not completely effective as the formation of the odor itself is not prevented and thus odor detection is not completely avoided. Some of the focus in the prior art has also been on the use of antimicrobial agents.
Thus although these materials provide some control of odors associated with bodily fluids, there still exists a need of further improvement in terms of odor control of malodors which are generated by the human body, or from bodily fluids such as perspiration, urine, faeces, menstrual fluids, vaginal fluids and the like.
It is an object of the present invention to provide articles, especially disposable absorbent articles, which deliver outstanding odor control, especially towards odor typically associated with bodily fluid. More particularly it is an object of the present invention to provide odor control benefits upon prolonged wearing time of an absorbent article.
It has now surprisingly been found that the addition of a pH buffering means on top of cationic polysaccharides enhances the malodor control properties of such cationic polysaccharides. Indeed, the combination of cationic polysaccharides, preferably chitosan materials, with acidic pH buffering means having a pH in the range of from 3.5 to 6.5 is much more effective in controlling odors, particularly those related to bodily exudates and bodily fluid. Thus the present combination is particularly suitable to be used in articles like disposable absorbent articles especially sanitary napkins, pantiliners or diapers.
More particularly, it has been surprising found that the addition of such an acidic pH buffering means on top of chitosan material results in a synergistic effect in terms of odor control. Indeed this combination gives more odor reduction than the odor reduction associated with the use of one of these two classes of ingredients alone at the same total level (either chitosan material alone or the absorbent gelling material alone) in an absorbent article coming into contact with bodily fluids.
Whilst not wishing to be bound by any particular theory, it is believed that the enhanced odor control benefits associated with the addition of acidic pH buffering means to cationic polysaccharides, especially chitosan materials, in an article, especially disposable absorbent article, is due to the ability of the pH buffering means to enhance the cationic character of the cationic polysaccharides and maintain it even under prolonged wearing time of the absorbent article and/or abundant bodily fluid discharge in the absorbent article. Typically the bodily fluids like menses have an initial pH within the range 6.5 to 7. This pH has the tendency to become more and more basic (within the range 7.5–8) upon ageing of the bodily fluid in the absorbent article. Indeed during normal wearing time, the menses discharge undergoes microbial and enzymatic degradation which results in the production of basic malodorous by-products like ammonia, indole. The use of an acidic pH buffering means will provide a more acidic pH environment and maintain it upon ageing of the menses in the article, typically upon prolonged wearing time. Such an acidic environment has the tendency to enhance the cationic properties of the polysaccharides present in the article and maintain these properties even upon prolonged wearing conditions. The cationic properties of the cationic polysaccharides would otherwise, in absence of such acidic pH buffering means, be neutralized due to increased alkalinity associated to bodily fluid.
Without to be bound by any theory, it is believed that it is the cationic properties of the cationic polysaccharides (preferably chitosan materials) that provide the odor control properties of such materials by multiple mechanisms.
Firstly, the odor absorption and retention characteristics of polysaccharides are due to the presence in the polymer structure of ionisable cationic functional groups. These groups are usually ammonium groups, a high proportion of which are in the salt form when the polymer is dry but which undergo dissociation and salvation upon contact with bodily fluid. In the dissociated state, the polymer chain will have a series of functional groups attached to it which groups have the same electric charge (e.g., —NH3+ +H3N—) and thus repel one another. This leads to expansion of the polymer structure, which, in turn permits further absorption of odorous molecules and thus the control thereof.
Secondly, the positively charged cationic groups of the polysaccharides will interact with negatively charged anionic function-bearing molecules present in bodily fluids, like the carboxylic groups of proteins or hydroxylic acid bearing entities like short chain acid (e.g., butyric acid). This will result in the formation of tri-dimensional net between cationic polysaccharides and such molecules with anionic groups (gelification of the bodily fluids). This gelification will entrap most odorous molecules (like lipids, acids) thereby controlling malodor.
Thirdly, cationic polysaccharides especially the aminopolysaccharides (chitosan materials) are believed to act as antimicrobial agents. Indeed the polysaccharides with their positively charged cationic groups will interfere with negatively charged surface of microorganism walls, thereby inhibiting the growth of such microorganisms or even killing such microorganisms. These cationic polysaccharides will also interfere with negatively charged surface of enzymes, thereby inactivating the enzymatic activity, which like the microbial activity, are otherwise responsible for the generation of malodorous components. The cationic polysaccharides like chitosan-based materials further act by their indirect antimicrobial activity by linking some of the microorganism nutriments like lipids and/or minerals.
Advantageously the addition of the pH buffering means as described herein, also results in improved safety and skin properties of the cationic polysaccharides, especially chitosan materials. Indeed, enhancing the cationic properties of chitosan materials translates in enhancing the binding to the negatively charged surface of the skin, in the case of rewetting occurrence (where chitosan can be brought in contact with the skin trough bodily fluid transport), thereby moisturizing the skin and providing a long lasting softness and fullness.
In a preferred embodiment herein the disposable absorbent articles herein have an apertured polymeric film topsheet. This topsheet contributes to further improve the odor control benefit.
In another preferred embodiment herein the disposable absorbent articles herein have a breathable backsheet. This contributes to a further improved odor control benefit. Even more preferred herein the disposable absorbent articles have both a breathable backsheet and an apertured polymeric film topsheet.
The present invention is preferably directed to disposable absorbent articles like pantiliners, feminine napkins, incontinent pads, diapers, tampons, interlabial pads, perspiration pads, surgical pads, breast pads, human or animal waste management devices and the like. Other articles suitable for use according to the present invention further include articles designed to be contacted with the body such as clothing, bandages, thermal pads, acne pads, cold pads, compresses, surgical pads/dressings and the like, body cleansing articles like impregnated wipes/tissues (e.g. baby wipes, wipes for feminine intimate hygiene), articles for absorbing perspiration such as shoe insoles, shirt inserts, and the like, and articles for animals like litters and the like.